Spinal implants such as interbody fusion devices are used to treat degenerative disc disease and other damages or defects in the spinal disc between adjacent vertebrae. The disc may be herniated or suffering from a variety of degenerative conditions, such that the anatomical function of the spinal disc is disrupted. Most prevalent surgical treatment for these conditions is to fuse the two vertebrae surrounding the affected disc. In most cases, the entire disc will be removed, except for a portion of the annulus, by way of a discectomy procedure. A spinal fusion device is then introduced into the intradiscal space and suitable bone or bone substitute material is placed substantially in and/or adjacent the device in order to promote fusion between two adjacent vertebrae.
Spinal fusion devices may be inserted during a spinal surgical procedure using an anterior, posterior, posterior lateral or extrapedicular approach. Certain spinal devices for achieving fusion using such approaches are also expandable so as to correct disc height between the adjacent vertebrae. Examples of expandable interbody fusion devices are described in U.S. Pat. No. 6,595,998 entitled “Tissue Distraction Device”, which issued on Jul. 22, 2003 (the '998 Patent) and U.S. Pat. No. 7,967,867 entitled “Expandable Interbody Fusion Device”, which issued on Jun. 28, 2011 (the '867 Patent). The '998 Patent and the '867 Patent each discloses sequentially introducing in situ a series of elongate inserts referred to as wafers in a percutaneous approach to incrementally distract opposing vertebrae to stabilize the spine and correct spinal height, the wafers including features that allow adjacent wafers to interlock in multiple degrees of freedom. The '998 Patent and the '867 Patent are both assigned to the same assignee as the present invention, the disclosures of both patents being incorporated herein by reference in their entirety.
Other spinal fusion devices may be inserted into the disc space using a lateral approach, as shown for example, in U.S. Pat. No. 7,749,269 which issued on Jul. 6, 2010 and is assigned on its face to Warsaw Orthopedic, Inc. (the '269 Patent) and U.S. Pat. No. 7,918,891 which issued Apr. 5, 2011 and is assigned on its face to NuVasive Inc. (the '891 Patent). The fusion devices described in both the '269 Patent and the '891 Patent are monolithic implants of fixed dimensions with neither having capability of expansion or tissue distraction once introduced into the intradiscal space. As such, the height of the implant upon insertion determines the final height of the corrected disc space. In addition, for implantation using a lateral approach, these implants are configured to be of length to be positioned in the disc space from one lateral side to the other such that the implant rests on the cortical rims of both opposing lateral sides of a vertebral body.
Consequently, there remains a need for an expandable interbody fusion device for insertion into the intradiscal space between opposing vertebrae using a lateral approach.